Antenna assemblies may be affixed to vehicles, such as airplanes, and configured to receive signals from a remote antenna assembly to provide services to the occupants of the vehicle during transit. For example, an antenna assembly may be configured to receive signals from a satellite. The satellite that is the source of the signals may be one that amplifies and redirects a received signal itself, or a satellite that intercepts a signal at a first frequency and retransmits at a second frequency. Particular examples of satellites that may be a source of signals to provide services include satellites associated with satellite radio services and satellites that offer broadcast television and pay-per-view channels. Such antenna assemblies configured to receive satellite radio and satellite television signals are conventionally non-transmitting antenna assemblies (i.e., a non-transmitting antenna assembly is one that is configured to receive signals from the remote antenna assembly, rather than being also configured to transmit signals back to the remote antenna assembly). When installed on an aircraft, such an antenna assembly may be used to provide in-flight entertainment services to airplane passengers.
In contrast, services offered to the occupants of a vehicle that offer two-way communications, such as receiving and sending emails, actively browsing the internet, or other forms of communication, and that are channeled through an antenna assembly that is affixed to a vehicle, require the antenna assembly to be configured to transmit signals to a remote antenna assembly.
The use of mobile antenna assemblies to transmit radiofrequency radiation to a remote target antenna assembly, such as a communications satellite in the Clarke belt, is regulated by the Federal Communications Commission (FCC). Exemplary regulation provides that earth stations on vessels (ESVs) that transmit in the 5925-6425 MHz (earth-to-space) frequency band to a geostationary satellite must maintain “a pointing error of less than 0.2° between the orbital location of the target satellite and the axis of the main lobe of the ESV antenna.” 47 C.F.R. 25.221(a)(1)(ii)(A). If the pointing error exceeds plus or minus 0.2 degrees—such as may occur when an antenna assembly is in motion—it may be required that transmissions from the antenna assembly are halted. For example, FCC regulations state that “all emissions from the ESV shall automatically cease within 100 milliseconds if the angle between the orbital location of the target satellite and the axis of the main lobe of the ESV antenna exceeds 0.5°, and transmission will not resume until such angle is less than or equal to 0.2°.” 47 C.F.R. 25.221(a)(1)(iii)(A). Halting transmissions between the antenna assembly and the radio signal source may incur service disruptions and, therefore, inconvenience aircraft passengers.
There is a need, accordingly, for a system and method that tracks a remote antenna assembly, and that tests, controls, and adjusts the alignment of an assembly (such as an antenna assembly) relative to the remote antenna assembly, such as a remote source of radiofrequency radiation.